The present invention relates to a new and distinct variety of nectarine tree named ‘NJN103’. Our new tree resulted from crossing ‘Fantasia’ (non-patented) nectarine as the seed parent with ‘NJN100’ (U.S. Plant Pat. No. 18,147) nectarine tree as the pollen parent. The new variety differs from seed parent ‘Fantasia’ in that the new variety has white flesh instead of yellow, and ripens about four weeks earlier. The new variety differs from pollen parent ‘NJN100’ in that the new variety produces larger fruit that ripen about 10 days later. The resulting tree was selected when growing in a cultivated area as the 42nd tree in the 54th row of Block K at a fruit research farm in Cream Ridge, N.J.